1. Field of Invention
The present invention relates to a semiconductor device which has a microstructure and a semiconductor integrated circuit over one substrate and which communicates with outside wirelessly. Moreover, the present invention relates to a method for manufacturing the semiconductor device.
2. Description of the Related Art
In recent years, research has been advanced on a micromachine system called MEMS. MEMS stands for Micro Electro Mechanical System, and this is sometimes called a micromachine, simply. A micromachine generally indicates a microdevice in which “a movable microstructure having a three-dimensional structure” and “an electric circuit having a semiconductor element” are integrated by using a semiconductor microprocessing technique. Unlike a semiconductor element, the microstructure has a movable part and a three-dimensional structure. Moreover, the microstructure can have a function of a switch, a variable capacitor, an actuator, or the like.
Since micromachines can control their own microstructures by electric circuits, it is considered that micromachines are not of central processing control type like a conventional device using a computer but micromachines can construct a distributed autonomous system that carries out a sequence of operations through an actuator and the like by processing information obtained by a sensor with the use of an electric circuit. A number of researches have been conducted on such micromachines (see Reference 1: Japanese Patent Laid-Open No. 2004-1201).
Meanwhile, with the progress of wireless communication techniques, development has been advanced on compact devices capable of sending and receiving information through wireless communication. Such a device includes a wireless chip for storing information in an electric circuit, a reader/writer for reading and writing information to be stored in the wireless chip, and a system for processing readout information and controlling the reader/writer. A wireless chip is also referred to as an RFID tag, an IC tag, a wireless tag, or various other names. A wireless chip is basically of nonbattery type and can carry out wireless communication with a reader/writer by obtaining drive electric power through an electromagnetic wave from the reader/writer. In recent years, a number of researches have been conducted on the wireless chips and identification information control techniques using the wireless chips.
It has been difficult to manufacture, by equivalent processes, a microstructure and a semiconductor element that form the above micromachine. This is because manufacturing of a microstructure needs a process of etching a sacrifice layer and so on, which are different from a process for manufacturing a semiconductor element.
Moreover, a semiconductor element often has a protective film and wiring thereover, and in such a case, how the microstructure is sealed is very important.
In this way, since different processes are necessary, there is a risk that the microstructure or semiconductor element may be broken so that the micromachine does not work. Thus, such a micromachine is currently put into practical use that the microstructure and the semiconductor element are manufactured in different steps.